The present invention is related to the invention described in copending application Ser. No. 11/860,834, filed concurrently herewith and titled FAST RUN-UP OF METAL HALIDE LAMP BY POWER MODULATION AT ACOUSTIC RESONANCE FREQUENCY which is incorporated herein by reference.
The present invention is directed to a method of decreasing the time from ignition to nominal (full) light output of a metal halide lamp.
Metal halide lamps for general lighting are efficient and produce high quality white light. However, the lamps require a few minutes to warm up to nominal light output because ballast output is focused mainly on steady-state operation. Shorter times to nominal light output would improve the applicability of metal halide lamps.
A faster run-up to steady state lamp operation can be achieved by overpowering a cold lamp. A temporarily high power level is not necessarily a problem, but because a cold lamp also tends to have a very low voltage, an excessively high current would be required to achieve the power needed (power=voltage×current). Moreover, care must be taken because excessive power or current can lead to thermal shock, electrode damage, and wall blackening, and lamps typically have a current limit during run-up to avoid these problems. Thus, light output does not reach nominal as quickly as desired.